Thread Tools
Feb 05, 2014, 11:30 AM
rip
ripacheco's Avatar
Thread OP
Build Log

Beginner's Xplorer II 3500 ST Lite


Xplorer II 3500 ST Lite.
My very first F3J/TD Competition Glider.


20 years ago I had two Olympic 650 later a full house glider*. I flew all those gliders in a slope just for fun. Last year I came back to to the hobby and got as a gift a modified Spirit glider which I have been using in local contests. Talk about accepting a gift and getting hooked!
* Don't remember the name of the glider except that it won the NATS before 1984

I am ready for the next step and, follwing the advice of some and the despite the warnings of others, I'm skiping any intermediate gliders and ordered a new Xplorer II 3.5

Since I have NEVER put together a non-woody model, this is going to be interesting.
Hopefully someone will read this and yell at me before I do something stupid!

Thanks to all that have answered my messages. I appreciate the advice.

Model Specs
  • Wingspan: 138 in (3500 mm)
  • Wing Area: 1176 inē (76 dmē)
  • Estimated Weight: 61 oz (1730 g)
  • Fuselage Length: 64 in (1625 mm)

RC Equipment
Electronic Diagram


Links

My Other Planes
Last edited by ripacheco; Apr 17, 2015 at 03:15 PM.
Sign up now
to remove ads between posts
Feb 05, 2014, 11:43 AM
Team Futaba
Silent-AV8R's Avatar
Plenty of threads in this sub-forum about the Xplorer series of planes. They all build very much the same. Most of the work is done for you. I'd suggest using the S3260SVi servo on ailerons and rudder. The 3173 is just more dead weight and the 3270 is more than up to the task. The 3173 is also tough to mount vertically, making it an issue to use for rudder. If you want the same format use the 3174SVi servo. Using that servo you could also use the servo frames that are available for the 3150 since they are physically the same size.

I'm using the 3173 on my flaps on my X2 4.0, easy to make a beam mount for them. You're going to like this plane a lot!!
Feb 05, 2014, 12:19 PM
rip
ripacheco's Avatar
Thread OP
Quote:
Originally Posted by Silent-AV8R
...The 3173 is also tough to mount vertically, making it an issue to use for rudder...
My powered airplane background messed me up on this one. The 3270 has 68% of the the 3173 torque and that was bugging me. I now understand that the rudder servo on a glider doesn't have to a lot of torque like it does on a pattern plane. You are correct about the mounting difficulties of putting a "wing-servo" on the fuse. I'll follow your advice on the rudder servo.
Feb 05, 2014, 12:47 PM
rip
ripacheco's Avatar
Thread OP

Futaba Servos


A disconcerting fact of buying Futaba Servos is how out of date many of the "official" web sites are:

http://rc.futaba.co.jp/english
http://futabarc.com

As of this date 2/5/2013, some or all of the servos that I'm buying from Tower Hobbies are missing on the sites above...

... makes research more difficult.
Feb 05, 2014, 12:59 PM
Team Futaba
Silent-AV8R's Avatar
All the current S.Bus servos show up on the Japanese site:

http://www.rc.futaba.co.jp/sbus/index.html

3270, 3173, 3174, etc.

The Futaba RC site is always behind, not sure why. I know that Hobbico only has one person to do ALL their website. So not really an excuse, but a reason at least.

The 3270 has all the torque you need for ailerons and rudder. Numerous people have flown the bigger Xplorers using the 3156 servo across the entire wing!! Yes, the soaring world is a little different from the power world when it comes to most everything.

Nothing wrong with using the 3173SVi for ailerons other than the fact that it places a bit extra weight outboard on the wing. Keeping all the wing servos the same does have some logic to it. I made an easy light mount for mine. Just cut the bottom tab off and mount to rails. Then glues the mounts in. The rails need to be 3/16" high.

As I noted above, the 3174SVi in the "normal" mount version of the 3173SVi and can be used in the widely available 3150 servo frame mounts.

Hope that helps.
Feb 05, 2014, 02:57 PM
Registered User
Avaldes's Avatar
Robert,

Good observation on gliders compared to power/aerobatic models. We tend to use the smallest and lightest servos we can for rudder. The aerodynamic forces are low and there isn't much room in the fuselage of a competition model. I use the 3156 for my rudders, but if you wanted to stick to SBUS then the 3270SVi would be a great choice.

The rest of your equipment list looks great.

-Aaron
Feb 05, 2014, 03:16 PM
rip
ripacheco's Avatar
Thread OP
Generally speaking... Is this correct ?

High to low servo torque list in F3J/TD gliders:
  • Elevator
  • Flaps
  • Aileron
  • Rudder

High to low servo speed list in F3J/TD glider
  • Elevator
  • Aileron
  • Rudder
  • Flaps


Quote:
Originally Posted by Avaldes
Robert,

Good observation on gliders compared to power/aerobatic models. We tend to use the smallest and lightest servos we can for rudder. The aerodynamic forces are low and there isn't much room in the fuselage of a competition model. I use the 3156 for my rudders, but if you wanted to stick to SBUS then the 3270SVi would be a great choice.

The rest of your equipment list looks great.

-Aaron
Feb 05, 2014, 03:32 PM
Flying What?!?
fnnwizard's Avatar
Quote:
Originally Posted by ripacheco
Generally speaking... Is this correct ?

High to low servo torque list in F3J/TD gliders:
  • Elevator
  • Flaps
  • Aileron
  • Rudder

High to low servo speed list in F3J/TD glider
  • Elevator
  • Aileron
  • Rudder
  • Flaps
Torque requirements are generally in the order below. The ail and rudder order could be flip-flopped, depending on the chord and control arm of the rudder. For the X2, the Ail horn will be plenty long enough.

Do a search for some of my posts in the X1 and X2 threads and you should find plenty of templates to help. One of the best mods you can do for the rudder is use a simple L bend with some .035 wire inserted into the hollow rudder pushrod and g10/carbon horn.

Due to the extreme overall low weights these X's are coming in at, it is even more paramount to keep as much weight as possible closer to the CG when building out.
You'll love the plane. There's nothing else close to the value of an X2


High to low servo torque list in F3J/TD gliders:
  • Flaps
  • Rudder
  • Aileron
  • Elevator
Feb 05, 2014, 03:42 PM
Registered User
Avaldes's Avatar
Personally I don't see the need for a fast rudder.

You should also consider that your observations about torque and speed should have consideration for the installation and the geometry of the linkage. One reason we use very fast servos on elevator is that during a zoom launch we are giving very large control inputs and the high speed servos help the control surface go from lock to lock quickly. The benefit can be better execution of the zoom.

The second design case for the elevator is the poke at the end of the landing approach. Again there can be some benefit to a faster elevator servo when you have low energy and need to make a correction to stab the nose at the spot.

In general I think we tend to use servos that have more torque than we really need. But that is ok. This probably helps overcome some of the friction in the linkages and the result can be better or more precise centering on the control surface. Hysteresis on pitch and roll can really stink up a good flying model.
Feb 05, 2014, 04:45 PM
Team Futaba
Silent-AV8R's Avatar
Aaron is dead on with his servo observations, especially about the torque. One consideration I look at is not just torque, but centering and then just how beefy the gear train is. Some guys are using very small servos on the flaps, but I use the a servo with a bit more heft to the gears (3173SVi).

Honestly, for you first plane none of the choices you have noted are wrong. All will work fine. The only absolute change need is to NOT use the 3173SVi with its side mount lugs for the rudder or elevator, just a pain to mount it. Torque and speed are fine for anything, it is just the mount that can cause issues.
Feb 05, 2014, 04:47 PM
rip
ripacheco's Avatar
Thread OP

On board equipment


This plane will have an S.BUS2 setup. Hopefully we wont need a complicated harness. I'm still debating putting a "plug-and-play" connector like a DB9 on the wing and fuse.
The on/off switch will be the magnetic sensor kind.
An altimeter will be used for setup and training.
Also pending is the decision about the battery. LIPOs should not be charged inside a plane but taking in/out a battery in a glider may be a chore. I need to measure the space I have for a battery and make sure get a battery of the right shape.
Last edited by ripacheco; Feb 05, 2014 at 05:53 PM.
Feb 05, 2014, 05:42 PM
Team Futaba
Silent-AV8R's Avatar
All I did was simply build a "Y" in the wing. A servo wire comes from each flap servo to the center panel where they join into a single plug that comes out of the center panel. looks like a single servo lead. That plugs into the fuse. Very easy.

Here is the fuse. All I did was glue the end of a servo extension into this plate. Made the plate from 1/16th ply.
Feb 05, 2014, 05:44 PM
rip
ripacheco's Avatar
Thread OP
Quote:
Originally Posted by Silent-AV8R
All I did was simply build a "Y" in the wing. A servo wire comes from each flap servo to the center panel where they join into a single plug that comes out of the center panel. looks like a single servo lead. That plugs into the fuse. Very easy.

Here is the fuse. All I did was glue the end of a servo extension into this plate. Made the plate from 1/16th ply.
You are right! with a Y inside the center wing and with S.BUS2 all i need is one plug not two as my schematic suggests.
Feb 05, 2014, 06:05 PM
Team Futaba
Silent-AV8R's Avatar
The 3270 only has a single plug in it so it cannot be put in a daisy chain. I plugged the rudder and elevator servos directly into the RX on port 2 & 3.

I put the wing into S.Bus

I put the battery and altitude sensor into S.Bus 2 on a Y. I use the Futaba Y which has a small block on it. The mag switch (not shown) goes between the RX and servo Y
Feb 05, 2014, 06:10 PM
Team Futaba
Silent-AV8R's Avatar
BTW S.Bus and S.Bus2 does not matter to the servos. You can interchange those. The telemetry MUST go into S.Bus2. All ports on both the R7008SB and R7003SB receivers are powered, so the battery can go anywhere.

I've got a lipo in my 4.0. SO far I charge in the plane, but I do it while I am sitting right next to it. Not a best practice, but I am OK doing it if I am right there with it. Personally, I'd get a 1450 or 2100 Hyperion LiFePO4 pack and stop thinking about the pack. I'd err on too big rather than too small right now. Trying to shave a few grams off using a smaller pack is not something you need to be concerned with at this point. Get it built and fly it. Your thumbs are the limiting factor now (and will be for some time). You are not going to lose a contest because you used a 1450 pack instead of an 800 pack.
Last edited by Silent-AV8R; Feb 05, 2014 at 06:23 PM.


Quick Reply
Message:

Thread Tools